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Due to strict regulations and the requirement to reduce greenhouse gas emissions, electric vehicles (BEVs) are a promising mode of transportation. The lithium battery is the most important power source for an electric vehicle, but its performance and life are greatly restricted by temperature. To ensure the safety of automobile operation and alleviate mileage anxiety, it is urgent to understand the current situation and predict the development and challenge of battery thermal management system. This work reviews the existing thermal management research in five areas, including cooling and heating methods, modeling optimization, control methods, and thermal management system integration for lithium batteries. Battery thermal management types include air-based, liquid-based, PCM-based, heatpipe-based, and direct cooling. Designing a better battery thermal management system not only needs to be optimized using algorithms on the model but also it uses intelligent algorithms for precise control to achieve safety and reduce energy consumption. This work also reviews the differences in thermal management systems between square and cylindrical batteries and summarizes the development trend of modularity in battery thermal management systems.

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Fuel spray and mixing in linear engines is coupled by dynamics, combustion, and gas exchange, which differs from that in conventional engines. This work presents a system simulation to reveal the multi-process coupling effect of injection position on the fuel spray and mixing of a free piston linear diesel engine (FPLE). A full-cycle fuel spray model which couples with dynamic, combustion, and gas exchange is established to predict the coupled effect on mixture formation. The results indicate that the variable injection position changes the FPLE motion through multi-process coupling effect, resulting in different boundary conditions for fuel spray and mixing. Relatively large injection advance position leads to more residual gas, fast speed, intense turbulence, low gas pressure, and temperature at the moment of injection for mixture formation. The earlier fuel injection generally makes the longer spray penetration, smaller Sauter mean diameter of droplets, less fuel impingement, faster fuel evaporation rate, and more evaporated fuel mass. However, too early injection does not support the above results. Suggesting that in order to achieve homogeneous combustion mode, the large injection advance position injection schedule operation is a good choice for the FPLE due to its long ignition delay duration for fuel atomization, evaporation, and mixing.

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